Nghiên cứu xây dựng hệ thống kích thích tế bào thần kinh và ứng dụng trong đánh giá đáp ứng không gian của tế bào vị trí hồi hải mã tt tiếng anbh

In this dissertation, a neural stimulation and recording sytem is developed for evaluating behavioral and spatial responses of mice from electrical stimulations with proper algorithms..

MINISTRY OF EDUCATION AND TRAINING MINISTRY OF NATIONAL DEFENCE

ACADEMY OF MILITARY SCIENCE AND TECHNOLOGY

TA QUOC GIAP

RESEARCH ON ESTABLISHING THE NEURAL STIMULATION SYSTEM AND APPLY FOR EVALUATING THE SPATIAL RESPONSE

OF HIPPOCAMPAL PLACE CELLS

Specialization: Electronic engineering

Code: 9 52 02 03

The abstract of dissertation

Hanoi – 2019

This dissertation was completed at:

ACADEMY OF MILITARY SCIENCE AND TECHNOLOGY

Scientific supervisors: 1 Dr Nguyen Le Chien

2 Dr Le Ky Bien

Reviewer 1: Tran Duc Tan, Ph.D., Assoc.Prof

Reviewer 2: Nguyen Minh Phuong, Ph.D., Assoc.Prof

Reviewer 3: Le Manh Hai, Ph.D

The doctoral thesis was examined by the Doctoral Evaluating Council

of Academy level held at Military Science and Technology at … on …,

…

This thesis can be found at:

1 The library of Academy of Military Science and Technology

2 Vietnam National Library

INTRODUCTION

1 The necessity of the project

Biomedical engineering is an applied science field, which connects different sciences from physics, chemistry, and biology to electrical, control, information, micro and nano technologies in order to provide biomedical solutions for improving human health Neural engineering is

an important subfield of biomedical engineering, which uses engineering techniques to treat, replace, or restore the functions of the neural system

It requires a device possessed controllable and stable properties for studying the mechanism of memory storing in the brain This plays an important role in a comprehensive understanding of physiological neural system Therefore, the development of systems that allow studying the physiology of the nervous system has highly practical applications

In this dissertation, a neural stimulation and recording sytem is developed for evaluating behavioral and spatial responses of mice from electrical stimulations with proper algorithms This system allows deeper understanding of the working principles of neurons and the brain In addtion, this is fundamental to study the structure and function of hippocampus, which may be associated with some neurodegenerative diseases such as Alzheimer’s, Amnesia, and Schizophrenia The practical exercises with their respective algorithms are first built on animals in order to develop the electrical stimulating and recording system for neurons The built stimulation system allows evaluating the electrical activity of neurons in their surrounding environment and the whole living organism correlations The electrical recording of neurons in hippocampus is fundamental to assess cells’ behavior in this place Importantly, specific working principles of the central nervous system will be elucidated to better understand feeling, memory, and autonomic

nervous mechanisms Therefore, the project “research on essurrtablishing

the neural stimulation system and apply for evaluating the spatial response

on hippocampal place cells” has a practical role in comprehensive studies of

neuronal physiology

2 Research objectives

- Developing a system for stimulating and recording the electrical activity

of neurons based on electronics engineering

- Building mathematical algorithms of neuronal stimulation for 4 practical exercises on mice

3 Research subjects and scope

- Research subjects: Neurons in a defined place of the Hippocampus is

electrically stimulated and recorded by using the built system Supporting devices and integrated programs for stimulating and recording are synchronous to form a complete system The stimulating and recording processes are automatically performed and analyzed

- Research scope: Developing a system that allows stimulating and recording neurons The stimulating programs associated with mathematical algorithms are integrated into the system Simulation and analyzing the results are based on electronic engineering

4 Research Methodology

Data collecting programs, simulations, and practical exercises are used

on mice for evaluating the system and exercises

5 Research contents and thesis structure

The main research contents:

- The overview of the electrical activity of neurons

- Modeling neurons with equivalent circuits and building algorithms of electrical simulations for neurons

- Evaluating the algorithms and system by simulation programs and practical exercises on mice

6 Scientific and practical significance

- Proposing proper stimulating parameters for studying subjects

- Developing a system for stimulating and recording the electrical activity

of neurons with 4 algorithms and 4 practical exercises on animals

- Performing simulations and practical exercises on mice to evaluate the proposed system and programs

- Providing fundamentals of medical issues for studying the central nervous system

CHAPTER 1: THE OVERVIEW OF THE ELECTRICAL ACTIVITY OF NEURONS

1.1 Membrane potential of neurons

Neurons are analogous to other cells, which have structural components

of cell membranes, nuclei and organelles The electrical activity of normal cells as well as neurons is highly related to the structure and characteristics of the cell membrane

1.2 Electrical nerve stimulation and medical significance

The development of nerve stimulating and recording system with proper algorithms is based on studying electrical properties of the cell membrane, the influence of electrical stimulating parameters, the response of cell membranes, and electrical stimulations in medical research

Figure 1.1 The change in membrane potential by the influence of

stimulating pulses

1.3 The response of cell membrane to the electrical stimulation

The plasma membrane potential changes when neurons are stimulated The membrane potential will return to its initial resting value after responding to the stimulus If the electrical stimulation is insufficient to create a transmembrane potential larger than a threshold, the membrane

will not be activated The amplitude and frequency of the electrical stimulation mainly influence the intracranial electrical stimulation, which are used to determine the stimulating threshold and maximum response

of cells In this work, electrical stimulating pulses are positive pulses with their variable amplitudes and frequencies

1.4 The recording methods of the neuronal action potential

The neuronal potential recording technique was developed in the 1940s During this period, extracellular microelectrodes were used to determine the potential characteristics of a neuron Recent studies of neurons associated with the neural stimulation and response have proven the relation of neurons in different places within brain Current technologies and equipment have also been developed for more accurate and convenient analyses of neuronal activities

1.5 Hippocampus and hippocampal place cells

Neuron studies have proven that hippocampal place cells play a vital role

in information store, short-term to long-term memory conversion and spatial orientation

1.6 The basic electronic circuit of neurons

To more comprehensively study and understand the action potential of cell membrane on electric stimulation, an equivalent conducting model of neurons has been modeled as an electronic circuit

1.7 Relevant research

- National: currently, there is not any neuronal stimulating system, which

allows both stimulating and recording the electrical activity of neurons

- Global: systems of manual neuronal stimulation and recording have been often found, however most of them are not synchronized and complete systems, which leads to the lack of accuracy in data analysis Some advanced systems can only describe the system function and stimulation results, but not evaluate the system

1.8 Chapter conclusion

CHAPTER 2: THE EQUIVALENT ELECTRICAL CIRCUITS OF NEURONS AND ALGORITHMS FOR ELECTRICAL NEURAL STIMULATION

2.1 The electronic circuit of neuron membrane and the investigation

of electrical stimulating parameters

The action potential of cell membrane can be analogously modelled as an electronic circuit

2.1.2 The simulation of electrical stimulating parameters with the Maeda-Makino model

Figure 2.3 The electronic circuit model of neurons by Maeda and Makino

2.1.3 Simulation results and discussions

The amplitude and frequency parameters of stimulation pulses are applied to the electric circuit for simulating the action membrane potential based on the Maeda – Makino model by the NI Multisim 14.0 progam

2.1.3.1 The relationship between current and the membrane potential of stimulation pulses at a fixed 80Hz frequency

The simulation results show that the membrane potential is directly

proportional to the stimulating intensity (Figure 2.6) However, the potential only dramatically rises over the current of less than about 10μA (the "bursting" range of potential response) before gradually increasing

in the current range from 10 to 110 μA In addition, while the stimulating current increases 110 μA, the potential increases suddenly and oscillates

R1 100kΩ

R2

200Ω

R3 100kΩ

XSC1

A B Ext Trig + + _ _ +

C1

2N3904

Q2 2N3906

Q5 2N3904

V1 5V

R4 1kΩ

R8 100kΩ R6 300Ω

XMM1

I1

0.07mA

C3 1µF V2 0.4V

Q4 2N3904

C4 0.2µF R5 10kΩ

Theoretically, this explains the risk of breakdown voltage of electronic components and the demolition of cell membrane

Figure 2.6 The change of potential depends on the stimulating intensity at the

Figure 2.7 The change of potential depends on the stimulating frequency at a

fixed intensity of 70μA

2.2 The stimulation and recording system for electrical activity of neurons

Figure 2.8 The illustration of the stimulation and recording system for

electrical activity of neurons

- The behavioral observation system: Consisting of a CCD camera for monitoring movements, behavior and positions of mice

- The stimulation system: a pulse generator establishes the form and parameters of pulses (Stimulator), which are sent to the isolator and DAC via USB 6501 before delivering to the nerve cells of mice by stimulation electrodes

-The recording system: The neuronal membrane potential is also recorded by stimulating electrodes The recorded signal from neurons is doubly amplified and processed by a signal processing unit (Plexon) The action potential is recorded and synchronously counted together with the stimulation pulse as well as the co-ordinates of the mice by control signals (TTL form) from the processing program installed in the computer to the Plexon system via USB device 6501

The developed system with integrated programs forms a complete device, which allows both electrically stimulating neurons and recording the neuronal membrane potential with designed task algorithms

2.3 Algorithms of electrical stimulations for neurons

2.3.1.1 The model of electrical stimulations for neurons with the NPT task

Isolator Stimulato r 6501 USB

Processing Circuit

Central processing system

Figure 2.10 The model of electrical stimulations and nose – poking responses

The input is the nose-poking behavior of the mice, which is transmitted via an optical sensor hiddenly located in a circular hole with the size diameter of 1.5 cm inside the chamber The sensor operating mode is set at a high logic status When the nose-poking happens, the sensor will be switched to a lower logic level The response signal from the sensor is sent to a processing circuit for counting the number of nose-poking if conditions of the task are completed as described in model 2.10

2.3.1.2 The electrical stimulations for neurons with NPT task

a) The significance of the NPT exercise

The NPT task algorithm is based on the strict requirements of reward conditions The intensity and frequency parameters of electrical stimulating pulses are evaluated from practical tasks in order to compare with the simulated parameters The NPT stimulation algorithm is shown

in Figure 2.11 with variable intensity and frequency parameters The program completely monitors the reward conditions and automatically rewards when the conditions of the task are reached The number of rewards or nose-poking behaviour is updated and visually displayed on a bar graph These values are stored in a file and objectively analyzed to evaluate the most appropriate parameters for spatial response tasks The expectation of the NPT task is to find the optimal parameters of the stimulating electrical pulse, which makes mice interest and poking the most in a period time of the task

Pt = 0; maxPt; chammui = 0; t = 0; maxT;

ptDelta = 0; tDelta = 0; delta;

countInterval = 0; interval Start

Chammui

End

Figure 2.11 Algorithm flowchart for the NPT task

2.3.2 The electrical stimulation models and algorithms for neurons with the spatial response task

2.3.2.1 The model of electrical stimulations for neurons with DMT task

Figure 2.12 The model for the DMT task

2.3.2.2 The constructions of electrical stimulation algorithms for neurons with the DMT task

a) The significance of the DMT exercise

The algorithm of the DMT task (Distance Movement Task) is based on strict requirements of reward conditions The movements of mice will be trained from easy to difficult requirements by the experimental tasks for asserting the optimal intensity and frequency parameters of the stimulating electrical pulses Those parameters were already determined

in the NPT task in the aforementioned part

2.3.2.3 The model of electrical stimulations for neurons with the RRPST

Figure 2.14 system for stimulating and recording the electrical activity of

neurons on the mice

The algorithm of electrical stimulations for the RRPST task

a) The significance of the RRPST exercise

The algorithm of the RRPST task (Random Reward Place Search Task) is based on the strict requirements of reward conditions The movement and reward motivation of mice are evaluated by the algorithm

of electrical stimulations for building the program and content of the RRPST task This experimental exercise will train the mice to move for searching rewards, which appear randomly The number of rewards or moving distances will be simulated to display the tracking path of mice and to update the reward number The obtained results are stored in a file and objectively analyzed for assessing the movements of mice in a particular space

b) The RRPST task

c) The algorithm flowchart of stimulations for the RRPST task

Pt = 0; t= 0; x t = x 0 ; y t = y 0 ; x zt = x z0 ; y zt = y z0 ; w z

deltaTime = 0; delayTime; maxwidth;

maxPt; maxT; taovungpt = false

Reading data

x t; yt

End

Start

Figure 2.15 The algorithm flowchart of stimulations for the RRPST task

The algorithm of stimulations for the PLT task

a) The significance of the PLT exercise

The algorithms of the PLT task (Place Learning Task) is based on strict requirements of reward conditions The movements of mice for searching fixed rewards will be trained by experimental exercises In addition, a program is built which can strictly monitor the reward conditions and automatically reward when the conditions are reached The number of rewards or moving distances will be simulated to display the tracking path of mice and update the reward number The obtained